Multilayer interventional catheter

ABSTRACT

The catheter comprises a catheter tube formed of two superposed tubular layers of materials which differ from one another. A tubular mediator layer is arranged between the layers to provide an adhesive anchorage for the layers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.08/908,060, filed Aug. 11, 1997, entitled INTERVENTIONAL CATHETER, whichis a continuation of U.S. patent application Ser. No. 08/581,084, filedDec. 29, 1995. Now abandoned and U.S. patent application Ser. No.09/053,969, filed Apr. 4, 1998, entitled CATHETER WITH MULTILAYER TUBE,which is a divisional of U.S. patent application Ser. No. 08/937,110,filed Sep. 24, 1997, now abandoned which is a continuation of U.S.patent application Ser. No. 081657,004, filed May 28, 1996, nowabandoned which is a continuation of U.S. patent application Ser. No.08/309,234, filed Sep. 20, 1994 now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to an interventional catheter comprising acatheter tube having two superposed layers of materials secured togetherand with mechanical properties differing from one another, a guidewirelumen in the catheter tube for the sliding fit of a guidewire, and aballoon with a distal end sealingly surrounding the catheter tubewhereby the catheter tube has an inner layer forming the guidewire lumenand an outer layer forming an outer surface of the catheter tube.

Over the wire catheters have been widely used for interventions such aspercutaneous transluminal cardiovascular angioplasty. A problem withthese catheters is that the guidewire may clog into the guidewire lumenof the catheter, whereby the guidewire may follow the balloon uponwithdrawal thereof after the inflation procedure thereby making itnecessary to re-insert the guidewire into the treated area of the bloodvessel for repositioning a balloon therein in case a second inflation isneeded. A further problem is that the catheter has to achieve anacceptable compromise between the requirements of some stiffness toassure good pushability and some flexibility to assure kink resistance.In addition, the catheter has to permit safe attachment of the balloonto the catheter tube.

Monorail® technology, which provides for an entry of the guidewiredistal of the balloon and an exit for the guidewire distal of theproximal end of the catheter tube, substantially reduces the risk of theguidewire clogging in the guidewire lumen because the length offrictional engagement between the guidewire and the guidewire lumen isstrongly reduced. That is also of great help in the handling of ballooncatheters for balloon exchange purposes. Though limited, the frictionand clogging problem is, however, still existent.

Two layer catheter shafts have been developed. For example, the documentWO 92/11893 describes an intra-aortic balloon apparatus comprising ahollow catheter in which is located an elongated member forming acentral lumen extending out of the catheter at the distal end thereof.An aortic pumping balloon is positioned over the elongated member; thedistal end of the balloon is bonded to a tip affixed to the distal endof the elongated member, and its proximal end is bonded to the distalend of the catheter. In order to achieve a balance of flexibility andremains and to avoid kinking, the elongated member is formed of an innerlayer comprised of a soft elastomeric material to impart flexibility tothe tubing and the outer layer is comprised of a hard plastic materialto impart structural support to the elongated member. This balloonapparatus cannot be loaded with a guidewire and moved into tortuousvessels with the guidewire loaded inside the elongated member as thefriction between guidewire and elongated member increases distinctivelywhen the elongated member is shaped into curves. There would betherefore the risk that a spiral wound guidewire could be captured inthe soft elastomeric plastic material of the inner layer of theelongated member. Although the outer layer of the elongated member thatis coextruded onto the inner layer is formed of nylon, a material whichis expected to be directly weldable to a wide variety of materials, thisballoon apparatus cannot be introduced into narrow vessels or narrowstenoses, nor can it be passed through narrow punctures to enter theblood vessels. This is because of the relatively large profile of thefolded balloon, due to the distal fixture of the balloon to theelongated member. The balloon is bonded to an intermediate tip elementwhich in turn is bonded to the elongated member.

The document EP 0 650 740 A1 shows a catheter comprising a catheter tubehaving two superposed layers of materials secured in relation to oneanother and with mechanical properties differing from one another, alongitudinal lumen in the catheter tube for the sliding fit of aguidewire, and a balloon with a proximal end and a distal end, thedistal end sealingly surrounding the catheter tube, whereby the cathetertube has an inner layer forming the longitudinal lumen and an outerlayer forming the outer surface of the catheter tube. In this catheter,the inner layer is formed of a material with lower friction coefficientthan the material forming the outer layer, whereby there is no more riskof having the guidewire clogging in the guidewire lumen of the cathetertube.

In terms of two layers catheter shafts, it has been observed that inpractical use the adhesion of the two layers of material was notabsolutely satisfactory. Although the coextrusion technology currentlyused for making such catheter shafts seems to involve close molecularinterpenetration of the materials forming the superposed layers of theshaft, it has been possible to observe separation of the two layers, forexample at the place of insertion of the shaft over the guidewire.Furthermore, tear test effected on such structures has shown that thetwo layers can separate under extreme conditions of stress on the shaft.

It is an object of this invention to propose an interventional ballooncatheter avoiding the aforesaid drawbacks. A further object of theinvention is an interventional catheter structure which is versatile andwhich provides a fully controllable and easy to manufacture assembly.Still a further object of the invention is an interventional low profileballoon catheter that can be safely operated on a guidewire and movedinto tortuous vessels and other extreme conditions.

Various multilayer catheters are known in the art. Reference is made toU.S. Pat. Nos. 4,627,844; 4,636,346; 5,403,292; 5,499,973; and5,538,510.

All documents cited herein, including the foregoing, are incorporatedherein by reference in their entireties for all purposes.

SUMMARY OF THE INVENTION

Accordingly, where the catheter comprises mediator layer means arrangedbetween the inner layer and the outer layer for the adhesive anchorageof the layers thereto, securing of the inner layer and outer layer isstrongly enhanced independently of their intrinsic capacity of adhesionto one another. The risk of a poor adhesion or the risk of a failure inthe adhesion of the two layers to one another is eliminated. The innerand outer layers may be chosen for their most appropriate mechanicalcharacteristics rather than for their capacity to adhere to one another.Because of the adhesive anchorage of the inner and outer layers on themediator layer means, the risk of separation of the two layers uponinsertion of the catheter tube over a guidewire is minimized. And theassembly of inner and outer layers is under control and thepossibilities of changing the flexibility of the assembly are improved;due to the adhesive anchorage on the mediator layer means, rigidity ofthe assembly is enhanced with the same basic inner and outer layers,whereas flexibility of the assembly may be mastered by safely acting onthe thickness of the inner and outer layers, with the resultingreduction in the profile of the catheter. As a result of the adhesiveanchorage of the inner and outer layers on the mediator layer means theassembly behaves like a unit; accordingly, the assembly may be safelygrabbed by the outer layer and tear tests are thus facilitated.

The inner and outer layers and the mediator layer means may be congruentin length, so that the catheter shaft can be produced in long tubeswhich may be cut at will to the appropriate length. Where the innerlayer, the mediator layer means and the outer layer are coextruded, acatheter tube is formed in a continuous process avoiding the need ofusing a core in the inner layer.

Where the inner and outer layers are substantially transparent and themediator layer means are contrasted with respect to the substantiallytransparent inner and outer layers, a visual control of the assembly isreadily available to further improve the manufacture.

Where the mediator layer means have mechanical properties differing fromthe mechanical properties of the inner and outer layers a further stepis achieved in the possibility of changing the lengthwise flexibilityproperties of the catheter.

When the inner layer is formed of a material with lower frictioncoefficient than the material forming the outer layer, there is no morerisk of having the guidewire clogging or being captured in the guidewirelumen of the catheter tube. Withdrawal and re-positioning of the ballooncatheter on a guidewire left in place at the site of treatment in thevessel system is rapid, safe and precise. Furthermore, the choice can bemade for materials for the inner and outer layers having the mostappropriate friction and kink resistance coefficients, while safeattachment of the balloon may be made at will on the outer layer whichis chosen without being influenced by the friction properties of theinner layer.

The mediator layer means may be formed on the basis of a low densitypolyethylene to offer superior adhesion performance in a wide variety ofconfigurations of the inner and outer layers and ease of processing onconventional fabrication equipment.

In a preferred form of the invention, the inner layer is made of apolyethylene or of a high density polyethylene, both of which assure anextremely low friction coefficient and an appropriate kink resistancecoefficient. In another preferred form of the invention, the outer layeris made of a polyamid to assure easy welding of the balloon and a goodstiffness at that level.

In sum, the invention relates to an interventional catheter comprising acatheter tube having two superposed layers of materials secured togetherand with mechanical properties differing from one another. A guidewirelumen is formed in the catheter tube for the sliding fit of a guidewire,and a balloon with a distal end sealingly surrounding the catheter tube.The catheter tube has an inner layer forming the guidewire lumen and anouter layer forming an outer surface of the catheter tube wherein itcomprises mediator layer means arranged between the inner layer and theouter layer for the adhesive anchorage of the layers thereto. The innerand outer layers and the mediator layer means may be congruent inlength. The inner layer, the mediator layer means, and the outer layermay be coextruded. The inner and outer layers may be substantiallytransparent and the mediator layer means may be contrasted with respectto the substantially transparent inner and outer layers. The mediatorlayer means may have mechanical properties differing from mechanicalproperties of the inner and outer layers. The inner layer may be formedof a material with lower friction coefficient than the material formingthe outer layer. The mediator layer means may be formed on the basis ofa low density polyethylene. The inner layer may be made of apolyethylene. The inner layer may be made of a high densitypolyethylene. The outer layer may be made of a polyamid.

These and other objects, features and advantages of the invention willbecome readily apparent from the following description with reference tothe accompanying drawings which show, diagrammatically and by way ofexample only, preferred but still illustrative embodiments of theinvention.

As will be realized, the invention is capable of other and differentembodiments and methods of construction, and its several details arecapable of modification in various obvious respects, all withoutdeparting from the invention. Accordingly, the drawing and descriptionare to be regarded as illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of an over the wireballoon catheter embodying the invention;

FIG. 2 is a longitudinal cross-sectional view of a Monorail® ballooncatheter embodying the invention; and

FIG. 3 is an enlarged cross-sectional view of a variant catheterembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The interventional catheter shown in FIG. 1 comprises a catheter tube 1formed of two superposed tubular layers of materials 2 and 3 with atubular mediator layer 4 arranged therebetween for the adhesiveanchorage of the layers 2 and 3 onto the mediator layer 4.

The tubular layers 2, 3 and 4 extend all over the length of cathetertube 1, being thus congruent in length, and the assembly of layersforming the catheter tube 1 may be obtained by the known coextrusiontechnology, i.e., by extruding simultaneously the inner layer 2 with themediator layer 4 and with the outer layer 3 thereover. Layers 2 and 3have mechanical properties differing from one another and, preferably,mediator layer 4 also has mechanical properties differing from themechanical properties of inner and outer layers 2 and 3.

Preferably, the inner layer 2 is formed of a material with lowerfriction coefficient than the material forming the outer layer 3. Forexample, the inner layer 2 may be formed of a polyethylene, preferably ahigh density polyethylene, whereas the outer layer 3 may be formed of apolyamid. The mediator layer 4 may be formed on the basis of a lowdensity polyethylene.

Preferably, the inner and outer layers 2 and 3 are substantiallytransparent, whereas the mediator layer 4 is contrasted with respect tothe substantially transparent inner and outer layers 2 and 3.

The catheter tube 1 has thus a longitudinal lumen 5 for the sliding fitof a guidewire exemplified by dotted line 6, which lumen 5 has a verylow friction coefficient, lower than that of the outer layer 3, and anon-kinking capacity while the outer layer 3 forms an outer surface ofthe catheter tube 1 and is easily weldable to the materials commonlyused for making balloons for angioplasty purposes and the like. Andtherebetween, the mediator layer 4 assures the best adhesive anchorageof inner and outer layers 2 and 3 thereto, the catheter tube 1 thusbehaving as a unitary element with differentiating properties at itsinner and outer levels.

Over the distal portion of the catheter tube 1 is positioned a balloon 7the distal end 8 of which sealingly surrounds the outer layer 3 ofcatheter tube 1, for example by welding.

A tube 9 is arranged over the catheter tube 1, at a radial distancethereof, thus defining an inflation lumen 10 for the balloon 7. Theproximal end 11 of the balloon 7 is welded onto the distal end of tube9.

The interventional catheter shown in FIG. 2 also comprises a cathetertube 12 having two superposed tubular layers of materials 13 and 14 witha tubular mediator layer 15 arranged therebetween for adhesive anchorageof the layers 13 and 14 onto the mediator layer 15.

The tubular layers 13, 14 and 15 extend all over the catheter tube 12and the assembly of layers forming the catheter tube 12 may also beobtained by the known coextrusion technology whereby inner tubular layer13 is extruded simultaneously with the mediator layer 15 and the outerlayer 14 thereover. Layers 13 and 14 have mechanical propertiesdiffering from one another and, preferably, mediator layer 15 also hasmechanical properties differing from the mechanical properties of innerand outer layers 13 and 14.

Preferably the inner layer 13 is made of a material with lower frictioncoefficient than the material forming the outer layer 14. For example,inner layer 13 may be formed of a polyethylene, preferably a highdensity polyethylene, whereas the outer layer 14 may be made of apolyamid. The mediator layer 15 may be formed on the basis of a lowdensity polyethylene.

Preferably the inner and outer layers 13 and 14 are substantiallytransparent and the mediator layer 15 is contrasted with respect to thesubstantially transparent inner and outer layers 13 and 14.

The catheter tube 12 has thus a longitudinal lumen 16 for the slidingfit of a guidewire exemplified by dotted line 17, which lumen 16 has avery low friction coefficient, lower than that of the outer layer 14 andwith a non-kinking capacity, whereas outer layer 14 forms an outersurface of the catheter tube 12 and is easily weldable to the materialscurrently used for making angioplasty balloons. And therebetween, themediator layer 15 also assures superior adhesive anchorage for inner andouter layers 13 and 14, the catheter tube 12 acting as a unit withdifferent properties at its inner and outer levels.

A tube 18 is affixed, for example welded, in parallel relationship tothe proximal portion of catheter tube 12, and this tube 18 extendsproximally of the catheter tube 12. The tube 18 defines an inflationlumen 19 for a balloon 20 the distal end 21 of which sealingly surroundsthe outer layer 14 of catheter tube 12, for example by welding. Theproximal end 22 of balloon 20 sealingly surrounds a proximal portion ofthe catheter tube 12 and a distal portion of tube 18, whereby theproximal portion of catheter tube 12 extends proximally out of theballoon 20 and the distal portion of tube 18 extends within the balloon20.

Variants are readily available. For example, the mediator layer may bemade of two superposed tubular layers of materials which differ from oneanother in order to respectively provide superior adhesive anchorage forthe inner and outer layers while assuring total adhesive anchoragebetween them. This configuration is advantageous for example to matchparticular flexibility requirements for the catheter tube or to assumeadhesive anchorage conditions which would be otherwise difficult for theinner and outer layers.

FIG. 3 shows such a configuration where the catheter tube 23 is formedof two superposed tubular layers of materials 24 and 25 with a tubularmediator layer 26 arranged therebetween and formed of two superposedadhesively anchored tubular layers 27 and 28, layer 27 being foradhesive anchorage of inner layer 24 and layer 28 for adhesive anchorageof outer layer 25. Within inner layer 24 is the guidewire lumen 29 forthe sliding fit of a guidewire exemplified by dotted line 30.

It will be evident from considerations of the foregoing that theMultilayer Interventional Catheter is now available, and may beconstructed using a number of methods and materials, in a wide varietyof sizes and styles for the greater efficiency and convenience of auser.

The above described embodiments of the invention are merely descriptiveof its principles and are not to be considered limiting. Furthermodifications of the invention herein disclosed will occur to thoseskilled in the respective arts and all such modifications are deemed tobe within the scope of the invention as defined by the following claims.

What is claimed is:
 1. An interventional catheter comprising: a cathetertube having at least two superposed layers of materials, including aninner layer and an outer layer, secured together and with mechanicalproperties differing from one another, a guidewire lumen in the cathetertube for the sliding fit of a guidewire, and a balloon with a distal endsealingly surrounding the catheter tube, whereby the inner layercomprises high-density polyethylene and forms the guidewire lumen, andthe outer layer comprises polyamide and forms an outer surface of thecatheter tube, wherein the catheter tube further comprises a mediatorlayer of low-density polyethylene arranged between the inner layer andthe outer layer for adhesive anchorage of the layers thereto.
 2. Theinterventional catheter according to claim 1, wherein the inner andouter layers and the mediator layer means are congruent in length. 3.The interventional catheter according to claim 1, wherein the innerlayer, the mediator layer means, and the outer layer are coextruded. 4.The interventional catheter according to claim 1, wherein the inner andouter layers are substantially transparent and the mediator layer meansare contrasted with respect to the substantially transparent inter andouter layers.
 5. A catheter comprising: (a) a rube comprising: (i) anoutermost layer comprising a polyamide having a first coefficient offriction; (ii) an innermost layer coextensive with the outermost layerand forming a guidewire lumen, the innermost layer comprising ahigh-density polyethylene having a second coefficient of friction whichis less than the first coefficient of friction; and (iii) a middle layerdisposed between the outermost layer and the innermost layer andaffixing the outermost layer to the innermost layer, the middle layercomprising a low-density polyethylene; and (b) a balloon with at least adistal end of the balloon sealed to the tube.
 6. The catheter of claim5, wherein the tube is formed by a process of coextrusion.
 7. A cathetercomprising: (a) a first tube comprising: (i) an outermost layercomprising a polyamide having a first coefficient of friction; (ii) aninnermost layer coextensive with the outermost layer and forming aguidewire lumen, the innermost layer comprising a high-densitypolyethylene having a second coefficient of friction which is less thanthe first coefficient of friction; and (iii) a middle layer disposedbetween the outermost layer and the innermost layer and affixing theoutermost layer to the innermost layer, the middle layer comprising alow-density polyethylene; (b) a second tube disposed about a portion ofthe first tube; and (c) a balloon with a distal end sealinglysurrounding the first tube and a proximal end sealingly surrounding thesecond tube.
 8. The catheter of claim 7, wherein the first tube isformed by a process of coextrusion.